The present invention relates to a semiconductor processing component and to a furnace for the production of semiconductors. In particular, the invention relates to treating processing components that are used to process semiconductors in low pressure chemical vapor deposition chambers.
Low pressure chemical vapor deposition (LPCVD) is a film forming process for the production of semiconductor devices. The process is used in the formation of layers such as silicon nitride, silicon dioxide and polysilicon on a silicon wafer substrate. Low pressure techniques, that is, in the range of 0.5-3 torr have advantages in terms of uniformity in processing. Typically in the process, a substrate is placed in a reaction chamber, which is heated and brought to a low pressure state. A reaction gas is introduced into the chamber and reaction material is deposited on the substrate either by reaction or by thermal decomposition of the reaction gas.
The deposition is conducted at temperatures between 550xc2x0 C. and 950xc2x0 C., at a pressure of about 1 torr using processing components that. include:a liner, process tube, shield, baffle, paddle, cantilever arm, carrier or boat made out of fused quartz. Since the processing components are at the same temperature as the wafer substrate, the components are coated at every run with a layer as thick as the layer deposited on the substrate. After many runs, each component is covered with a thick film build-up. The film build-up causes a stress from the coefficient of thermal expansion (CTE) difference between silicon (2.9 ppm/xc2x0 C.) or silicon nitride (5.0 ppm/xc2x0 C.) and quartz (0.5 ppm/xc2x0 C.). Eventually, this stress induces cracking in the surface of the quartz. The surface cracks weaken the component and generate particles that decrease process yield. Components such as wafer carriers or boats and related cantilever arms are more prone to crack formation because they are cycled from the process chamber temperature to room temperature with each run to allow loading and unloading of wafers.
There is a need to reduce the adverse effects of micro cracks in the surface of processing components.
The invention relates to a semiconductor processing component comprising a quartz body characterized by silicon oxide filled micro cracks and to a semiconductor furnace system, comprising the quartz body. The processing component is treated by applying a silicon layer onto the component body and oxidizing at least a portion of the silicon to silica to fill the micro cracks in the surface of the component body.
In another aspect, the invention is a heat treatment process, comprising preparing a quartz processing component by cleaning the component to remove a build up silicon layer and to expose micro cracks in the surface of the component and to etch the micro cracks into trenches. A silicon layer is applied onto the processing component body and at least a portion of the silicon is oxidized to silica to fill the trenches in the surface of the component body. The processing component is then installed within a processing chamber of a chemical vapor deposition furnace. A substrate to be treated is loaded into the processing chamber and a treatment gas is supplied into the processing chamber to form a film on the substrate surface.